Mexican security forces are searching for about 50 migrants who were kidnapped from a commercial bus, authorities said Wednesday.

The kidnapping took place in the central state of San Luis Potosi, the Attorney General’s Office there said. The bus, whose two drivers were also missing, was discovered further north in the border state of Nuevo Leon on Tuesday, it added, without specifying when the incident took place.

President Andres Manuel Lopez Obrador told a press conference the National Guard has been deployed to try to locate the migrants.

On Tuesday, Nuevo Leon’s security agency tweeted that nine migrants – aged from 18 to 35 and from Honduras and Venezuela – had been rescued.